1. Field of the Invention
The present invention relates to a signal correction apparatus which adjusts the characteristics of an input signal.
2. Description of the Related Art
The development of a signal characteristic adjustment apparatus is in progress. This signal characteristic adjustment apparatus provides a desired listening environment (for example, indoor transfer characteristics, a head-related transfer function, and volume) by adjusting the characteristics (for example, volume, frequency characteristics, phase characteristics, and tone characteristics) of an input signal (for example, a speech or audio signal) using digital signal processor (DSP).
For example, an equalizer apparatus is available. This apparatus can adjust a level (for example, a power or signal amplitude) for each frequency band. Upon adjusting the level of a digital signal, when the level is raised, it may exceed a maximum level of a digital signal system, and that signal may be unwantedly clipped.
For this reason, the equalizer apparatus which raises the level of a digital signal executes level control for declining the level of an input signal over an entire frequency range, converts the input signal into an analog signal, and then amplifies the level of the analog signal by an amount declined in the processing of the digital signal.
Conventionally, in order to prevent deterioration of the signal-to-noise ratio due to raising/declining of the level, the level of an input digital signal is declined based on a maximum level change so as not to be clipped (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2002-345075).
However, conventionally, since the level is declined only by a fixed amount, an excessive volume drop occurs depending on input signals.
The conventional signal characteristic adjustment apparatus declines the level of a digital signal so as to prevent the digital signal from being clipped. However, since the level is declined only by a fixed amount, an excessive volume drop may occur.